A ring binder mechanism retains loose-leaf pages, such as hole-punched pages, in a file or notebook. It has ring members for retaining the pages. The ring members may be selectively opened to add or remove pages or closed to retain pages while allowing the pages to be moved along the ring members. The ring members mount on two adjacent hinge plates that join together about a pivot axis. A housing loosely supports the hinge plates within the housing and holds the hinge plates together so they may pivot relative to the housing. The housing generally has a central portion and lateral sides extending downwardly from the central portion along both sides. The hinge plates are disposed between the lateral sides of the housing, which retain the hinge plates in the housing.
When the rings are closed, it is desirable to bias the ring members to remain in their closed position. Even slight movement of the ring members toward their open position threatens unintentional release of loose-leaf pages. Slight movement of the ring members toward their open position also presents a risk that the pages will get caught on the tips of the ring members and rip as the pages are moved along the rings from one ring member to the other. Thus, the ring members are typically biased toward their closed position by a spring or other mechanism that applies a clamping force that holds the ring members together when they are in their closed position. An operator may typically overcome this force by manually pulling the ring members apart or pushing them together. Levers may also be provided on one or both ends of the housing for moving the ring members between the open and closed position.